Numerous control methods for automated storage and retrieval systems have been developed, particularly for permitting storage and retrieval of containers of articles such as cases or boxes in a warehousing arrangement. Such control methods usually inventory and locate the containers in horizontally and vertically disposed storage racks. The control method controls an automated stacker crane or the like which is movable horizontally and vertically along one side of the storage rack and has a carton transfer mechanism associated therewith which can remove the carton or container from the storage rack and deliver it to a shipping or use location. Such arrangements are conventionally tied to a central controller or computer which stores the inventory locations and control instructions for the stacker crane. When an order for a particular container is received in the controller, it moves the stacker crane to the associated position in the storage rack and retrieves the particular container. Such systems are generally suitable for handling only a low quantity of containers or articles, and typically handle large containers and not individual small articles.
Dispensers which are particularly suitable for dispensing a high volume of high-demand articles are also known, and examples thereof are disclosed in U.S. Pat. Nos. 4,000,821 and 5,271,703. The structural complexity and overall cost of these dispensers, however, do not make them cost effective for handling articles and filling orders where the articles are in low demand, particularly where there is a large inventory of different low demand articles from which particular individual articles must be selected to fill an order.
Accordingly, there is a need for an automated storage and retrieval system which can handle a large quantity of different low demand articles, typically small articles, and more desirably a combination of high, medium and low demand articles, in large enough quantities to automatically dispense particular articles needed to fulfill a large number of orders. In view of this need, the Assignee hereof developed an improved order pick system as described in application Ser. No. 09/019,274 (hereafter the '274 application), filed Feb. 5, 1998, and the entirety of the disclosure of the '274 application is herein incorporated by reference. A brief description of the system of the '274 application is provided below in conjunction with FIGS. 18 and 19.
Referring to FIGS. 18-19, the automated article storage and retrieval system 610 includes an order pick system 611 which cooperates with an article storage system 612. The filled orders from the pick system 611 are typically supplied to a packaging station 613. The system 610 also includes a conveyor system 645 for moving article-receiving orders through dispensing zones 641, 642, 643, and a tote replenishment station 614 wherein stacks of typically small articles (such as CDs, video cassettes, etc.) are moved into storage cells in boxlike totes. The storage system 612 stores individual articles 616 in vertical stacks within cells 618 which in turn are defined within movable containers or storage totes 630 (FIG. 19). Each stack normally contains only identical articles stacked vertically on top of one another.
The storage totes 630 are disposed on tiered rows of shelves defined by storage racks 631 associated with the storage system 612, and can be accessed using automated storage and retrieval devices 635 such as conventional stacker cranes or carousals. The totes 630, in the illustrated arrangement, provide articles to three different dispensing zones 641, 642, 643 which respectively handle low demand articles, high demand articles, and high/moderate demand articles. The high demand zone 642 contains known high-speed dispensers for dispensing the articles onto an order-collecting conveyor system. The high/moderate demand zone 643 contains moderate demand dispensers for dispensing articles onto the order-collecting conveyor system 645. The low demand dispensing zone 641 contains a gantry-type dispenser system 655 which can access a large number of different low demand articles 616 contained in pick totes 500 disposed in preassigned locations adjacent the order-collecting conveyor system 645 to permit transfer of individual articles from the totes to preassigned order collecting areas on the conveyor system (FIG. 19). The low demand picking zone 641 typically involves several gantry subzones 652 arranged along the conveyor system 645. Each gantry subzone 652 includes a respective gantry mechanism 655 and a plurality of active pick face totes 500 supported along at least one side of the conveyor system 645, and the cells 618 of the pick face totes have a plurality of articles stacked therein which can be accessed by the gantry mechanism 655. The gantry mechanism 655 moves to a specific cell of a specific pick face tote, removes the ordered article 616 from the cell 618, and transfers the article for deposit onto a preassigned area of the conveyor system 645. This article retrieval process is repeated several times within one subzone and sequentially within the several subzones as the conveyor system moves the order-collecting areas sequentially through the subzones to permit filling of a single order with the desired low demand articles. The conveyor system 645 may also move the order receiving area sequentially through the high and moderate demand dispensing zones 642, 643, if necessary, to receive ordered articles from these zones into the preassigned order receiving areas. After the orders have received the articles from the order fulfillment system 611, then the order receiving areas are sent to the packaging system 613 for packaging and shipping.
It is an object of this invention to provide a method for controlling an article storage and retrieval system which can efficiently and substantially automatically fulfill a plurality of orders with a plurality of low-demand articles selected from an inventory containing a very large number of different low-demand articles. A further object of the invention is to provide a method, as aforesaid, wherein stacks of articles are efficiently handled and located within the article storage and retrieval system so that movement of order fulfillment devices are efficiently operated. A still further object of the invention is to control the fulfillment of orders requiring high, moderate and/or low demand articles.
In the controlling process of the present invention, according to one aspect thereof, a large number of different orders each identifying one or more different type article thereon are inputted into a control system to create an order list for the next order fulfillment cycle. The individual articles stored in the system are also assigned an identification code which reflects the frequency of demand of the specific type article, which identification code is automatically determined from historical order analysis. The different type articles are contained in stacks disposed in individual cells of upwardly-opening containers known as totes. A first plurality of active pick totes are associated with individual article dispensing zones, and other inactive pick totes are disposed in replenishment zones positioned adjacent the individual dispensing zones. Based on historical order analysis, and an analysis of the available articles contained in the active totes, sufficient articles are transferred into inactive totes so as to anticipate the next order list, and the inactive totes are interchanged with selected active totes so as to position needed articles in the dispensing zones prior to start-up of the next order fulfillment cycle. The controlling process positions the different type articles in the totes according to the demand frequency identification, and positions the active pick totes in a series positional relationship through the dispensing zone which is based on an analysis of the different demand frequency identifications so as to provide for substantially uniform load level distribution (i.e., uniform dispensing of individual articles from a dispensing zone), taking into account the relative movements of the dispensing device and the order receiving device which are cooperatively associated with the series of active totes disposed in the dispensing zone. The controlling method maintains an identification of the quantity and location of each different type article, including those in storage totes and those contained in active or inactive totes as disposed respectively in the dispensing zone and the associated replenishment zone, thereby permitting automated control over not only the replenishment of different type articles to and from the dispensing zone, but the actual picking of different type articles from the dispensing zone for filling the individual orders on the order list.
Other objects and purposes of the invention will be apparent upon reading the following specification and inspecting the accompanying drawings.